General-Purpose Mail Filter

7.1 Special Configuration Data Types

In addition to the usual data types (see Statements in GNU Mailutils Manual), mailfromd configuration
introduces the following two special ones:

time interval specification

The time interval specification is a string that defines an
interval, much the same way we do this in English: it consists of one
or more pairs ‘number’-‘time unit’. For example, the
following are valid interval specifications: